docs: def parse_bool(val):
      """Parse a bool value.
  
      Handles a series of values, but you should probably standardize on
      "true" and "false".
  
      >>> parse_bool('y')
      True
      >>> parse_bool('FALSE')
      False
  
      """
      true_vals = ('t', 'true', 'yes', 'y', '1', 'on')
      false_vals = ('f', 'false', 'no', 'n', '0', 'off')
  
      val = val.lower()
      if val in true_vals:
          return True
      if val in false_vals:
          return False
  
      raise ValueError('"%s" is not a valid bool value' % val)